In the pharmaceutical industry, a machine is used to fill capsules with a granular pharmaceutical product, and which comprises a conveyor device moving continuously along a given path and having a number of pockets, each for receiving a respective bottom shell of a respective capsule; at least one container for the product; and a metering wheel mounted to rotate continuously about a substantially vertical longitudinal axis.
The metering wheel has a number of metering devices, each of which travels with the metering wheel along a portion of said path, in time with a respective bottom shell, to withdraw the product from the container and feed the product into the bottom shell.
Each metering device comprises a metering cylinder for receiving the product from the container; a drop chute for unloading the product in the metering cylinder into a respective bottom shell; and a piston which defines the bottom of the metering cylinder, and is moved along the metering cylinder, to and from a feed position to feed the product to the drop chute, by a cam follower roller on the piston engaging a cam.
Known machines of the above type have several drawbacks, mainly on account of engagement of the cam by the cam follower rollers moving each piston into the feed position to feed the product to the relative drop chute, regardless of whether the corresponding pocket on the conveyor device contains a bottom shell or not.
Another drawback of known machines of the above type is that, when using two containers containing different granular products, engagement of the cam by the cam follower rollers may not allow for selectively metering the product of only one of the containers into the bottom shells.